1. Field of the Disclosure
The disclosure herein relates generally to obtaining cores from a formation and estimating one or more properties of interest downhole.
2. Description of the Related Art
To obtain hydrocarbons such as oil and gas, wells (also referred to as “wellbores” or “boreholes”) are drilled by rotating a drill bit attached at a bottom end of a drill string. The drill string typically includes a tubular member (made by joining pipe sections) attached to a top end of a drilling assembly (also referred to as the “bottomhole assembly” or “BHA”) that has a coring drill bit (or “coring bit”) at the bottom end of a drilling assembly. The coring bit has a through-hole or mouth of a selected diameter sufficient to enable the core to enter into a cylindrical coring barrel (also referred to as a “liner”) inside the drilling assembly. One or more sensors are placed around the core barrel to make certain measurements of the core and of the formation surrounding the wellbore drilled to obtain the core. The length of the core sample that may be obtained is limited to the length of the core barrel, which is generally a few feet long. Such systems, therefore, are not conducive to continuous coring (coring beyond the core barrel length) or for taking measurements of cores longer than the core barrel length. To core for an extended wellbore length, the coring operation is stopped in order to either retrieve the core from the core barrel or to raise the drill string above the top of the core to disintegrate the core with the drill bit before continuing the drilling of the wellbore. It is, therefore, desirable to continuously core and obtain measurements to estimate one or more properties of the core and of the surrounding formation to obtain tomograms of the cores and of the formation, and to selectively store core samples from more than one depth, substantially without stopping the drilling operation.
Therefore, there is a need for an improved apparatus and method for coring and making measurements relating to various properties of the cores and the formation.